Friday, May 26, 2006

Make that ten most ‘beautifully interesting’ birds (part I)

A while back I was tagged by Coturnix to perpetuate the 10 bird meme. As you’ll know if you’ve heard of this project, it was started by John (of A DC Birding Blog) and has so far produced over 50 responses (go here to see them). To be honest I’m not that interested in or excited by the human concept of what is considered ‘beautiful’, so I’ve added my own slant to this and have decided to cover instead a selection of birds that can be considered ‘beautiful’ in terms of what they tell us about evolution. We might call them ‘beautifully interesting’ birds. Given that there are about 10,000 extant bird species to chose from, my selection is pretty much random and hardly representative. I simply sat down and wrote about the first ten ‘beautifully interesting’ species that popped into my head. Then I started writing about them… and because I ended up producing a lot of text I’m going to split it over several posts. Here we go, I hope you enjoy. I haven’t finished with late-surviving Mesozoic synapsids yet, by the way.

1. Flying steamer-duck Tachyeres patachonicus

Admittedly, all ten of my most ‘beautifully interesting’ birds could be anseriforms, as I have a special affinity for waterfowl. But I’ll limit myself to one of my favourites, the Flying steamer-duck.

The most widely distributed of the four Tachyeres species*, T. patachonicus inhabits both the fresh and marine waters of the Falklands and southern Patagonia and Tierra del Fuego. While all other steamer-ducks are flightless, T. patachonicus is (obviously) not, and in contrast to its flightless relatives it has proportionally bigger pectoral muscles and lower wing loadings. But what makes the species especially interesting is that some males within the species actually have wing loadings that are too high to permit flight, and are thus flightless (Humphrey & Livezey 1982, Livezey & Humphrey 1986). So, within a single species, there are both flighted and flightless individuals. It is almost as if the species is poised in the transition to full flightlessness, and indeed both morphological and genetic studies (Corbin et al. 1988) agree that T. patachonicus is the most basal member of its otherwise flightless genus. Flighted and flightless individuals are known to have also occurred in some recently extinct anseriform species, incidentally.

* One species, T. leucocephalus, was only described in 1981.

But there’s more. Steamer-ducks are notoriously pugnacious. Heavy-bodied and robust compared to other ducks, they have tough skin, a massive head and neck, and are equipped with keratanised orange knobs on the proximal parts of their carpometacarpi. Both sexes use these wing knobs in territorial fights and displays. Fighting males grab each other by the head or neck and then whack each other vigorously with the wing knobs, and fights can last for up to 20 minutes. Both birds sometimes submerge during the fight, and come up still fighting. This reminds me of scenes in films where super-heroes and villains (e.g. Spider-man vs Doc Oc) fall off buildings together and continue to battle even while plummeting toward the ground, but that’s just me. An aggressive steamer-duck approaches an ‘enemy’ by either adopting the so-called submerged sneak posture (only the top of the head and back and tail tip are visible), or by ‘steaming’ noisily across the surface (the ducks charge at speed, throwing their wings like the paddles of a paddle-steamer, hence the vernacular name).

Here’s where things get especially cool. Other waterbirds are shit-scared of steamer-ducks, and ‘mass spooks’ of other duck species, grebes and coots have been recorded when these birds saw or heard the local T. patachonicus. You see, they attack and kill other waterfowl. A particularly detailed steamer-duck attack on a Shoveler Anas platalea was recorded by Nuechterlein & Storer (1985a), and I here summarise the account they describe on p. 89.

A male steamer-duck caught a male shoveler by the neck and began pounding it with its wing knobs. The female steamer-duck displayed excitedly nearby. The shoveler was held beneath the water, then yanked up and beat some more. The male steamer-duck took a break and displayed with his female, then he went back to the shoveler, grabbed it again by the neck and proceeded to beat it another 15-20 times. By now the shoveler was looking pretty limp (though still alive). It was pecked at and released and both steamer-ducks displayed together again, and the male steamer-duck now began to move away from the shoveler. The shoveler now began to move (slowly) toward the shore and eventually got there. Then it died. ‘Examination of the specimen disclosed several broken bones, hemorrhages in the lower neck region and massive internal bleeding at the base of the right leg’ (p. 89). During the course of their study at Laguna de la Nevada, Santa Cruz Province, Argentina, Nuechterlein & Storer (1985a) picked up the carcasses of six ducks that had definitely been killed by steamer-ducks within a single week. Why steamer-ducks are so aggressive remains the source of debate (Murray 1985, Livezey & Humphrey 1985a, b, Nuechterlein & Storer 1985b). But don’t mess with them.

2. Shovel-billed kingfisher Clytoceyx rex

A New Guinea endemic, C. rex was named in 1880 and it’s been studied by such ornithological luminaries as Forshaw, Beehler and Diamond (see blog on the Odedi). A halcyonid kingfisher and close relative (or even member) of the kookaburra group, it’s strikingly big (c. 30 cm long) and with a fantastic broad, flattened bill. This is driven hard into the ground with a vigorous action and it’s apparently used quite literally as a shovel. As is the case in some other birds that sometimes handle hard-shelled prey, the edges of its tomia are scopate: that is, they possess tiny brush-like structures (Gosner 1993). Poorly known and rarely seen, it apparently does most of its foraging at dusk. Mostly preying on worms, the species also eats lizards, snails and insects. It’s sometimes called the Earthworm-eating kingfisher. It’s cool.

3. Wrybill Anarhynchus frontalis

Tetrapods generally have symmetrical bodies, but there are a few awesome exceptions. Among birds, the best is the Wrybill, a mid-sized charadriid wader endemic to New Zealand. Its short bill, about 25 mm long, is remarkable and unique in being curved at its tip toward the right, and always to the right. To forage, the bird tilts its head to the left and explores beneath stones and rocks, scraping off arthropods, fish eggs and other objects. It always moves clockwise around a stone. In The Life of Birds, David Attenborough suggested that this unique behaviour might only have been able to evolve in a place where terrestrial predators were absent: the Wrybill keeps watch for aerial predators while foraging, but it doesn’t need to watch for terrestrial ones.

Apart from its bill, the Wrybill isn’t much to look at. It’s grey and white with a black breast band and white forehead. Phylogenetic studies find it to be close to Charadrius (Chu 1995), and thus probably a core charadriid (traditional Charadriidae is not monophyletic (Ericson et al. 2003)). Wrybills migrate from North Island to South Island to breed. The total world population is only 4000-5000.

4. Blue-capped ifrita Ifrita kowaldi

Originally described by DeVis in 1890 as Todopsis kowaldi, Ifrita was independently ‘discovered’ by Walter Rothschild in 1898 and named by him Ifrita coronata. A passerine endemic to moist montane forests on New Guinea, Ifrita is remarkable for two reasons. Firstly, nobody really knows what it is and over the years it’s been classified in several different, disparate passerine families. It’s been allied with warblers, log-runners, and corvids. Secondly, it’s poisonous. I’ll repeat that for those people who hadn’t heard it before. It’s poisonous. While it’s nowadays reasonably well known that pitohuis (a group of six species of pachycephalid passerines, also endemic to New Guinea) produce batrachotoxin in their skin and feathers, it was shown in 2000 that Ifrita does too (Dumbacher et al. 2000). It’s thought that the poisons present in these birds are sequested from poisonous insect prey, but last I heard this was still under debate.

As for why the birds are poisonous, it’s been widely suggested that the poisons they harbour function as a chemical defence against snakes, raptors and predatory mammals. However, they may also protect the birds against parasites (Mouritsen & Madsen 1994). Incidentally, (1) it seems that not all pitohui species are poisonous (although further study is required to be absolutely sure about this), (2) that another New Guinean passerine, the Rufous shrike-thrush Colluricincla megarhyncha, also produces batrachotoxin, and (3) that multiple other non-poisonous New Guinea passerines (including some other pitohuis) may mimic poisonous pitohuis and therefore gain protection from predators too (Diamond 1992, Dumbacher & Fleischer 2001).

More ‘beautifully interesting’ birds to come soon, among other stuff.

The image above is a montage cobbled together from various images I took off the web. So far as I could tell none of them needed permission for use. For the latest news on Tetrapod Zoology do go here.

1 Comments:

Anonymous said...

Darren,

Great stuff. I am a birder, but I'm learning things from this. There are birds that are no-kidding toxic? I did not know that!

Of course, they'd have to be from New Guinea...

Brief digression: I have a friend who hates Jared Diamond. Well, to be precise, he hates Diamond's popular writings. He's familiar with several of the fields Diamond writes about, and has found a lot of sloppiness and factual errors.

He asked me once, what the heck is it with this guy? How can he be so arrogantly certain about such a wide range of knowledge?

And I said, well, he's a New Guinea ornithologist.

They really are a breed apart. Two reasons, I think. One, because the environment is so challenging. Birding in New Guinea is really freaking hard. Most of the country is still literally trackless jungle, laid over some really rugged mountains. Once you get in the interior, there are no decent roads, and the local languages change every few miles. It's hardcore. And the personalities it attracts tend not to be shy and retiring.

Of course, other places are just as rough -- the Congo, say. But New Guinea is additionally challenging because the birds you meet are weird. So weird that even today, it's often hard to tell what their affinities are, or why they do what they do. To be a good ornithologist in that environment, you can't just do a lot of observing and then check off against the textbook. You have to be a broad and original thinker. All in all, Diamond is fairly typical of the breed.

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About Me

Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. YOU ARE CURRENTLY AT A VERY OLD VERSION OF TET ZOO: for modern articles, go to: http://blogs.scientificamerican.com/tetrapod-zoology/ And check out the Tet Zoo podcast at tetzoo.com!